Piston operated slide valve

ABSTRACT

A piston has a stem projecting outwardly from a cylinder. The outer end of the stem is provided with a longitudinal slot extending through it, in which a valve slide fits and projects from the opposite sides of the stem. The exposed sides of the slide are flat and parallel. Secured to the cylinder is a stationary block that has a flat surface engaging one side of the slide. A floating block also has a flat surface engaging the other side of the slide. Mounted in the stationary block is a pair of studs that straddle the stem beside the slide and also extend through openings in the floating block. The blocks are provided with passages that register with a passage through the slide when the latter is in one of its positions. A pressure bar is slidably mounted on the studs and has a projection between them engaging the floating block in the central longitudinal plane of the slide. Springs are mounted on the studs and press the bar projection against the floating block.

O Unlted States Patent 1 13,570,540

[72] Inventors Alexander Crawford Mclnnes; FOREIGN PATENTS Em!" Ch 1#g173,471 11/1960 Sweden 251/62 Pi g Robert Kush, wllkins 287,339 11/1952Switzerland 251/174 m 341,368 11/1959 Switzerland 277/163 $59; 3839221,137,070 1/1957 France e 1 451 Patented Mar. 16, 1971 'f' Nels [73]Assignee Mine Safety Appliances Compan AS81810"! Exammer-Michaelp. SturmPittsburgh, Attorney-Brown, Murray, Flick and Peckham ABSTRACT: A pistonhas a stern projecting outwardly from a [54] VALVE cylinder. The outerend of the stem is provided with a longitudinal slot extending throughit, in which a valve slide fits and n 137/625-481 projects from theopposite sides of the stem. The exposed 251/621 251/17 sides of theslide are flat and parallel. Secured to the cylinder [111- 1 1/06, is astationary block that has a flat surface engaging one side of F161 25/00the slide. A floating block also has a flat surface engaging theofSearch other side of the slide Mounted in the stationary block is a 6-3 277/163, 205, pair of studs that straddle the stem beside the slideand also ex- 156, 157 tend through openings in the floating block. Theblocks are rovided with assa es that re 'ster with a assa e throu [56]References cited he slide when t he la tter is in or i e of itspositions. a pressu e UNITED STATES PATENTS bar is slidably mounted on thestuds and has a projection 3,160,015 12/1964 Charlton et a1. 137/625.68Xbetween them engaging the floating block in the central 1on- 3,294,11912/1966 Hunt 137/625.48 gitudinal plane of the slide. Springs aremounted on the studs 3,462,244 8/1969 Leisey 137/625.48X

/\TIT 111111111111 and press the bar projection against the floatingblock.

Patented March 16, 1971 3,570,540

2 Sheets-Sheet 1 I I INVENTORS. A. claw/2220 Mcl/VNES M I el /57m F.KLAGES, JQ.

I "L BY ,eoazers. X05

ATTORA/EKS.

PISTON OPERATED SLIDE VALVE it is among the objects of this invention toprovide a piston operated slide valve of simple construction, in whichthe slide is sealed against leakage in a simple manner.

The preferred embodiment of the invention is illustrated in theaccompanying drawings in which:

FIG. 1 is an end view of the valve;

FIG. 2 is a sideview;

FIG. 3 is an enlarged fragmentary plan view;

FIG. 4 is plan view of the valve slide mounted in the piston stem;

FIG. 5 is an enlarged longitudinal section taken on the line V-V of FIG.1; and

FIG. 6 is a cross section, partly broken away, taken on the line Vl-Vlof FIG. 5.

Referring to the drawings, a fluid'pressure cylinder has a body 1 withan integral end wall and with a removable end wall formed by a mountingplate 2 attached to the open end of the body by means of screws 3.inside the cylinder there is a piston 4 (FIG. 5) which is spacedslightly from the surrounding wall of the chamber by a pair of sealingrings mounted in axially spaced annular grooves in the piston. Each ofthese rings is formed from a flexible plastic channel 5 openinglaterally toward the adjacent end of the piston. An endless coil spring6 tits in each of the channels and holds its sidewalls firmly againstthe piston and cylinder. These sealing rings not only seal the piston,but also prevent it from engaging and wearing against the surroundingcylinder wall.

Secured to the center of one side of the piston by a screw 8 is a stem 9that extends out through a central opening 10 in the integral end wallof the cylinder. The slight clearance between the stem and the wall ofthe opening is sealed by a ring 11 having the same construction as thosejust described. The portion of the stem in the cylinder is round, but ithas an extension that extends away from the cylinder which is reduced inthickness to provide it with two more or less flat surfaces 12 and 13equal distances from the stem axis. This part of the stem also isprovided with a longitudinal slot 14 that extends through it andcontains a valve slide 15 that projects slightly from the flat sides ofthe stem.

The slide is made of a slippery plastic, such as Teflon, and its exposedsides are flat and parallel. One of these sides engages the flat surface17 of a stationary block 18 that is secured to the adjoining end wall ofthe cylinder by means of a pair of screws 19. The other flat side of theslide is engaged by the flat inner surface 20 of a floating block 21that is held in place by a pair of studs 22. The studs are rigidlymounted in the stationary block at opposite sides of the piston stem,beside the slide as shown in FIGS. 1 and 3. These'studs extend, with aslight clearance, through openings in the floating block, which canslide on them and engage flat against the slide when the slide is flatagainst the stationary block. The slide has two positions, an innerposition and an outer position, which are determined by movement of thepiston from one end of the cylinder to the other. The studs are locatedabout midway between the two positions of the slide. To move the piston,fluid under pressure is delivered to the cylinder either through apassage 23 communicating with the space between the piston and theintegral end wall of the cylinder, or through a passage 24 that leadsinto the other end of the cylinder.

The slide is provided with a passage through it connecting its flatsides asshown in FIG. 5. When the slide is in its inner position asshown in FIG. 5 the ends of this passage are closed by the two blocks,but when the slide is in its outer position the passage registers withthe inner ends of a pair of aligned passages 27 extending through theblocks. All of these passages are in the central longitudinal plane ofthe slide and piston stem and therefore are located midway between theopposite sides of the two blocks.

Each block may also be provided with a passage 29 located not only inthe plane just mentioned but also in a plane perpendicular to it andcontaining the axes of the two studs. When the slide is in its innerposition, the inner ends of the two passages 27 and 29 in each block areput in communication with each other by a groove 30 in the adjoiningside of the slide as shown in FIG. 5. When the slide is moved to itsouter position these grooves connect the inner ends of passages 29' witha third pair of passages 31 through the blocks, all the passages in eachblock being equally spaced.

In order to press the floating block against the slide and to press theslide against the stationary block, a stiff pressure bar 33 is slidablymounted on the portions of the studs projecting from the floating blockasshown best in FIGS. 1 and 3. This bar is pressed against the floatingblock by means of springs 34 mounted on the studs and compressed thereonby nuts 35 threaded on the outer ends of the studs. For best results,Belleville springs are preferred. Since the width of the pressure bargenerally is a little greater thanthe distance between the inner andouter passages 27 and 31 of the floating block, thesides of the bar areprovided with openings, such as notches 37, through which loosely extendtubes 38 connected to the outer ends of the passages. A tube 39connected to the outer end of the central passage; 30 in the floatingblock extends loosely through a central opening 40 in the pressure bar.The tubes therefore do not interfere with movement of the bar.

It is highly desirable that the two blocks press flat against theadjoining flat sides of the slide in order to form good seals so thatleakage will not occur between the slide and the blocks. Accordingly,most of the pressure bar is spaced from the floating block, but midwaybetween its ends it is provided with projections 42 between thetube-receiving openings therein. These projections engage the outersurface of the floating block and are convex when viewed from the sideof the bar so that they will have a substantially line contact with theblock in the central longitudinal plane of the slide. As a result, evenif the springs do not exert equal pressure against the opposite ends ofthe bar, all of the spring pressure will be applied to the floatingblock only along a line in the central longitudinal plane of the slideand therefore the block will always be pressed flat against the slide.There is slight clearance between the slide and the surrounding stem,i.e. there is -a loose fit between them, so that the stem cannotinterfere with the slide engaging flat against the stationary blbck.Con-- sequently, the slide always fits flat against the stationaryblock, and the floating block is always pressed flat against the slide.This insures good seals at opposite sides of the slide.

if the pressure bar did not have its projections 42 but ehgaged flatagainst the floating block, it would apply pressure unequally across theslide if the springpressure on the two slides were not uniform. If fourstuds and two pressure bars were used, the likelihood of unequalpressure on the slide would be increased further. The single bar withthe central projections disclosed herein assures uniform pressure of theblocks throughout the areas of the flat sides of the slide.

lclaim: l. A piston-operated slide valve comprising a cylinder having anend wall provided with a central opening therein a piston disposed inthe cylinder, a piston stem secured to the piston and slidably mountedin said opening, said stem extending outwardly away from said end walland provided outside of the cylinder with a longitudinal slot extendingthrough the stem, a valve slide fitting in said slot and projecting fromthe opposite sides of the stem, the exposed sides of the slide beingflat and parallel, the piston being movable back and forth in saidcylinder to move said slide between two fixed positions, a stationaryblock secured to said end wall and having a flat surface engaging one ofsaid flat sides of the slide, a floating block having a flat surfaceengaging the other flat side of the slide, a single pair of studsmounted in he stationary block and straddling said stem beside'theslide, the floating block being provided with openings therethroughslidingly receiving said studs, the slide having a passage therethroughconnecting its flat sides, said blocks having aligned passagestherethrough registering with said slide passage when the slide is inone of said fixed positions, a pressure bar slidably mounted on the porin the central longitudinal plane of the slide, springs mounted on thestuds in engagement with the outer surface of said bar, and nuts screwedon the studs and compressing the springs to press said bar projectionagainst the floating block,

2. A slide valve according to claim 1, including a tube connected to theouter end of the passage in the floating block, and said pressure barbeing provided with an opening for said tube.

3. A slide valve according to claim 1, in which each of said blocks isprovided with a plurality of passages in said longitudinal plane, andtubes are connected to the outer ends of all of the passages in thefloating block, said pressure bar being provided with a plurality ofopenings through which said tubes extend.

4. A slide valve according to claim 3, in which there are three of saidtubes and said openings in the pressure bar are at opposite sidesthereof and at its center, there being two of said bar projections withone of them located between each side opening and the center opening.

5. A slide valve according to claim 1, in which said springs areBelleville springs.

6. A slide valve according to claim 1, including axially spaced sealingrings encircling said piston and spacing it from the surrounding wall ofsaid cylinder, each of said rings consisting of a laterally openingflexible plastic channel, and an endless coil spring fitting in thechannel.

1. A piston-operated slide valve comprising a cylinder having an endwall provided with a central opening therein, a piston disposed in thecylinder, a piston stem secured to the piston and slidably mounted insaid opening, said stem extending outwardly away from said end wall andprovided outside of the cylinder with a longitudinal slot extendingthrough the stem, a valve slide fitting in said slot and projecting fromthe opposite sides of the stem, the exposed sides of the slide beingflat and parallel, the piston being movable back and forth in saidcylinder to move said slide between two fixed positions, a stationaryblock secured to said end wall and having a flat surface engaging one ofsaid flat sides of the slide, a floating block having a flat surfaceengaging the other flat side of the slide, a single pair of studsmounted in he stationary block and straddling said stem beside theslide, the floating block being provided with openings therethroughslidingly receiving said studs, the slide having a passage therethroughconnecting its flat sides, said blocks having aligned passagestherethrough registering with said slide passage when the slide is inone of said fixed positions, a pressure bar slidably mounted on theportions of said studs projecting from the floating block and, having aprojection between the studs engaging the floating block in the centrallongitudinal plane of the slide, springs mounted on the studs inengagement with the outer surface of said bar, and nuts screwed on thestuds and compressing the springs to press said bar projection againstthe floating block.
 2. A slide valve according to claim 1, including atube connected to the outer end of the passage in the floating block,and said pressure bar being provided with an opening for said tube.
 3. Aslide valve according to claim 1, in which each of said blocks isprovided with a plurality of passages in said longitudinal plane, andtubes are connected to the outer ends of all of the passages in thefloating block, said pressure bar being provided with a plurality ofopenings through which said tubes extend.
 4. A slide valve according toclaim 3, in which there are three of said tubes and said openings in thepressure bar are at opposite sides thereof and at its center, therebeing two of said bar projections with one of them located between eachside opening and the center opening.
 5. A slide valve according to claim1, in which said springs are Belleville springs.
 6. A slide valveaccording to claim 1, including axially spaced sealing rings encirclingsaid piston and spacing it from the surrounding wall of said cylinder,each of said rings consisting of a laterally opening flexible plasticchannel, and an endless coil spring fitting in the channel.